Electrical-disturbance-eliminating system



Oct. 11, 1927. 1,645,1

l. G. WILSON ELECTRICAL DISTURBANCE ELIMINATING SYSTEM Filed Dec. 5

p My

Patented 0a. 11, 1921.

were at IRA G. WILSON, OE BROOKLYN, NEW YORK, ASSIGNOR T0 WESTERN ELEG'EEIC (20M. PARTY, INCORPORATED, 0F NEW YORK, 13%; Y., A. CGBPGRATIOH 03'' NEW YORK.

ELEGTRIGAL-DEBTURBANCE-ELIMINATING SYSTEM.

Application filed December as, 1825. serial Ito. 7%,185.

This invention relates to electrical disturbance eliminating systems and more particularly to the elimination of noise from speech transmission systems.

One of the principal sources of external interference encountered in telephone or carrier transmission systems is inductive interference caused by induction or conduction currents from power transmission lines being picked up by the telephone lines which are m exposed locations with respect to the power lines. it has heretofore been proposed to overcome interference of this sort by permanently connecting filters or other tuned circuits in the noisy line. This has .the inherent disadvantage of always removing the same frequency of the voice currents corresponding to the noise frequency present in the line. Furthermore this arrangement rei moves the voice frequency even though the noise frequency is not present.

in accordance with the present invention, these disadvantages are overcome by providing tuned relays having their reeds set into vibration by the prolonged noise frequency and only in the event of the presence of a prolonged disturbing frequency or a composite noise on the line will the reeds of the relays build up suihciently to connect.

in theirassociated neutralizing circuits.

Referring to the drawings, Fig. 1 is a diagrammatic view of a repeater system showing one embodiment of the invention, and Fig. 2 illustrates a simplified arrangement of the invention as applied to a repeater system.

In the drawings TE represents a telephone or toll exchange from which extends a transmission line consisting of conductors 1 and 2. These conductors are connected to line windings 3 and 4 of hybrid coil 5. A balancing network N, simulates the transmission line and the associated equipment. A uni-directional repeater 3,, preferably of the electron discharge type, has its in ut circuit 6 bridged across the line win g of hybrid coil 5, while the output circuit '2 is inductively connected to the subscribers line 8 by means of windings 9 and 10 of hybrid coil 11. The hybrid coil 11 is provided with windings 12 and 13 which are included in the subscribers line 8. This line is also balanced at one end with a network N while the other end of the line is connected to the subscribers equipments. This description pertains to the transmission of speech from the telephone exchange T. E. through the re peter R, to the subscriber S. For transmission in the opposite direction a similar uni-directional repeater it, has its input cir- 1 cuit 14c bridged across the line windings of hybrid coil 11 while the output circuit 15 is inductively connected to the transmission conductors l and 2 through windings l6 and 17 of hybrid coil 5.

It often happens that in the geographical region through which the transmission conductors 1 and 2 extend there are high tension power lines, such as railway electrification systems, overhead trolley lines, power lightmg circuits, or other high tension current carrying conductors which are in parallel relation with respect to the transmission conductors 1 and 2. These high tension systems induce interference or noise in the transmission conductors and since the range of frequencies of the noise is within the range of speech frequencies, both the noise and voice frequencies are transmitted over the line. Now, in the case of a repeater system, these noise frequencies are amplified together with the speech frequencies and the resultant amplified noise frequencies in the output of the repeater cause interference in the subscribers circuit.

To overcome this interference, a slow-act ing relay 18 is bridged across the transmission conductors 1' and 2. This relay is pro vided with a tuned reed 19 which may be tuned mechanically in any desirable manner, for instance, by a weight 20 being adjusted to a position on the reed to tune the reed to a desirable frequency or range of frequencies. This reed is connected to the line conductor 2 so that in its normal osition it forms an open circuit for the tuned? am lifier.

The mechanically tuned relay is a apted till to form an automatically operating device to connect a tuned filter or ampl fier, or oth er correcting circuit to the transmission line in which the noise disturbance is 'present. As

shown in the drawing it is preferable to construct the corrective circuit along the line of a uni-lateral device sothat the output will not feed back into the outgoing transmission circuit. The tuned amplifier comprises an input circuit in which one line conductor 21 is normally connected in open circuit POSI- tion by means of the contact adjacent to the tuned reed 19. The other input conductor 22 is connected to the conductor 1 by the transmissionline. Bridged across these conductors are inductance 23 and capacity 24 having values determined by the range of fre-, quencies corresponding to the-range of frequencies to which the tuned reed 19 is responsive. A condenser 25 is also connected in series with the primary winding 26 of transformer 27 for filtering purposes. One end of the secondary winding 28 of transformer 27 is connected to the grid electrode 29 of the electron discharge device 30, while the other end is connected to one side of the filament 31 through battery 32. The secondary winding of transformer is made variable or tapped to make it possible to vary the amplification. A battery 32 is connected in series with the filament and grid to impress a negative potential on the grid electrode. A battery 33 is connected in the filament circuit to render the filament 31 incandescenta The plate electrode 34 is connected to one side of primary winding 35 of transformer 36 while the other side is connected to battery 37 to impress a positive potential on the plate electrode. The secondary winding 38 of transformer36 is bridfid across the output circuit 7 of repeater Available inductance 39 and a variable capacity 40 are connected between the secondary winding 38 and one of the conductors 7. These adjustable elements are located in the output of the tuned amplifier for purposes of changing the phase and am plitude of the frequencies transmitted through the electron discharge device 30.

For the purpose of this invention, it is assumed that besides the voice frequencies being transmitted over the line conductors 1 and 2, thereare also noise frequencies being transmitted together with the voice frequencies. Since the noise frequencies are well within the rangev of the voice frequencies,v it is apparent that both types of frequencies will be transmitted over the repeatered line and the noise frequencies will cause considerable annoyance to a subscriber listening on the subscriber line 8.

While the ranges of these types of frequencies are similar, there is a marked difference in their character, since voice frequencies are generally momentary impulses,

shown in the drawing,

while the noise frequencies are im ulses of relativel long duration. This diligrence is taken a vantage of in accordance with this invention by providin the tuned relay arrangement above descn ed comprising winding 18 and reed-armature 19, which Will be unaffected by momentary or speech im ulses and will take a considerable length of time to build up when the reed is set into vibration by the relatively long continued noise frequencies. However, when the reed is vibrated by a particular noise frequency present in t e line, it will continue to vibrate while that frequency is present and in due time will vibrate to such an extent that the contact will be closed and the particular frequency will be fed into the input of the tuned amplifier. The connection of the amplifier to the transmission line causes the noise frequencies to traverse a parallel ath, one through the repeater circuit R an the other through the tuned amplifier. However, the ad ustments in the tuned amplifier change the phase and amplitude of the frequencies so that the out ut of the amplifier neutralizes the noise Frequencies passing through the repeater R and while there is noise on the lineup to the point of the outut of the repeater R the neutralizing efect of the tuned am lifier upon the output 95 of the repeater R su stantially removes the noise frequencies from the hue after this point.

The character of the noise or interference induced in the transmission line is generally composite, that is the noise is not confined to a single frequency but ma comprise a wide range of frequencies. I or this purpose, it is preferable to bridge a number of tuned reeds across the transmission line, ad- 1o5 justing the reeds mechanically to different frequencies or ranges of frequencies. As another relay 41 has the tuned reed 42 capable of being vibrated by a particular range of frequencies to which it is tuned. This reed is similarly connected to an input circuit 43 of a tuned amplifier TA having its output circuit connected to conductor 7. Since the operation of this circuit is the same as the one previously de- 1 scribed, except for the range of frequencies to which it is tuned, it needs no further description.

Any number of relays may be bridged across the transmission line 1, 2 to take care of a wide range of noise frequencies. Then in the event of a com osite noise bemgpresent on the line, on y those relays which are tuned to the particular frequencies present on the line will be operated to connect in their. res ctive correcting circuits or tuned ampli era. In this arrangement only those frequencies which lie withthe corrective circuits will only be connected to the transmission line when the corresponding frequencies to which they are responsive are present.

While any number of relays may be connected to the line to associate tuned amplifiers with the line, it is apparent that other corrective circuits may be associated with the relays to accomplish the same purpose. For instance as shown in Fig. 2 the tuned reed 44- is grounded at one end to a battery 45. The tuned reed 4.4 also carries a carbon button 46 which is connected to the primary winding at of an induction coil 48. lhe secondary winding 49 is connected to the output circuit of repeater R, in the same manner as explained in connection with Fig. l. in the-operation of this circuit the noise frequencies on the line will operate the re lay which in turn will vibrate the reed 4:4 to which the carbon button 46 is attached. l'he operation of the relay acting on the reed will build up its efiects and cause it to vibrate. ln other words, the property of inertia of the mechanical system will produce a time lag so that the actuating current may be applied for an appreciable length of time. 'This will be the case for a noise current which lasts for a relatively long time. On the other hand, a voice current of the same frequency will be essentially transient in character, and will neither last long enough to start vibration, nor if the reed is already in vibration long enough to change the mode of vibration. This inertia may be used therefore to distinguish between noise currents and voice currents of the same frequency. Assuming that the reed 44 is set into vibration by the continued noise frequency, this will generate a current in the carbon button 46 of the same frequency at which the reed is vibrating and proportional to the amount of vibration of the reed. The output of this system is then a current of the same frequency as the disturbing noise and of the same amplitude. lhis may be fed back into the circuit as was described in connection with Fig. 1. If necessary or desirable amplitude and phase shift controls may be inserted in the circuit to obtain an absolute balance so that the subscribers circuit may be reasonably quiet. This arrangement forms a simple and economical device for the removal or neutralization of the noise frequencies present in the line. Furthermore, the relative insensitiveness of the carbon button for low energy input gives a further protection against removing the voice frequency, since the efi'ect of these frequencies will be very small due to the inertia of the reed.

While the invention has been disclosed with respect to a repeater circuit, it is apparent that the invention can be applied to other speech transmission systems. Furthermore, the application of the property of inertia described above is not confined to purely mechanical means. Similar results may be obtained by electrical means, for instance, by replacing the tuned reed orcarbon button with an amplifier having a long time constant. Such an amplifier is described by Bennett and Peters in the Journal of the American institute of Electrical Engineers, of March 1922, entitled Resistance neutralizationj By increasing the time constant of this type of amplifier the voice impulses would never build up and therefore could not balance themselves, but a continuous noise impulse would.

-What' is claimed is:

l. lin a telephone transmission system, comprising a telephone line subject to interference from an external source, a normal line, interconnecting means between said lines, a neutralizing circuit connected to said normal line, and means in said telephone line operated by said interference to connect said neutralizing circuit to said telephone line.

2.111 a telephone transmission system, comprising a telephone line subject to int-erference from an external source, it normal line, interconnecting means between said lines, a neutralizing circuit normally con-v nected to said normal line, and a slow-actin relay in said telephone line, said relay being actuated by the interference in said line to operate contacts to connect said neutralizing circuit to said telephone line.

3. In a telephone transmisison system, comprising a telephone line subject to interference from an external source, a normal line, interconnecting means between said lines, a neutralizing circuit connected to said normal line, and a relay having a tuned reed connected across said telephone line, said relay being actuated by interference present in said telephone line to operate said reed and connect said neutralizing circuit to said line.

a. la combination, a line over which speech impulses are transmitted and subject to steady disturbing currents, a normal line connected to said disturbed line, a neutralizing circuit superimposed on said normal line, and mechanical means associated with said disturbed line acted upon by said disturbing currents to connect said neutralizing circuit to said disturbed line while still maintaining efiective for the speech innpulses the connectionbetween said lines.

5. In combination, a normal line, a disturbed line, means for connecting said lines for the transmission of speech, a correcting circuit, input and output terminations for said correcting circuit, said output being connected to said normal line, and means operated by the disturbance said disill . impulses, and means operable K turbed line to connect to said disturbed line. 6. In combination, a line over which speech and noise frequencies are transmitted, a normal line, interconnecting means between said lines, a correcting circuit, input and output terminations for said circuit, said out ut being operatively associated with said normal line, and tuned means in said first line .operable by said noise frequencies to connect said in ut to said line, said means being unaifected y said speech frequencies.

7. In combination, a line for the transmission of speech, said line having induced therein interfering frequencies within the speech range, a trunk lme, interconnecting means between said lines, a correcting circuit, andvibrating means operable by said interfering frequencies to uild up sufficiently to interconnect said correcting circuit to said line.

8. In combination, a line for the transmission of speech, said line havin induced therein interfering fre uencies within the speech range, a normal line, interconnecting means between said lines, a correcting circuit, and a vibrating reed operable by said interfering frequencies, the inertia of said reed being built up by the continued interfering frequencies to interconnect said correctin circuit with said transmission line.

9. combination, a line for the trans mission of speech, said line having induced therein interfering frequencies within the speech range. a normal line, interconnecting means between said lines, a correcting circuit, and a vibrating reed operable by said interfering frequenc1es, the inertia of said reed introducing a time lag in the operation of said relay to connect said correcting circuit to said transmission line.

10. In combination, a line over which speech and noise impulses are transmitted, a normal line, interconnecting means between said line. a correcting circuitnormally connected to said normal line, a slow-acting relay'connectcd to said first line, said relay differentiating between short impulses of speech and continued noise impulses, a tuned reed vibrated by said continued noise said input termination connected to said normal means operated by saidnoise impulses to.

by said reed I to connect said correcting circuit to said line to remove said noise im ulse's, said reed being non-operative by said speech impulses.

11. In combination, a toll line over which speech and noise impulses are transmitted, a normal line, a repeater connecting said line, a correcting circuit permanently connected to said repeater and said normal line, and mechanical means bridged across said toll line, said means being operable by said IIOISQ HHRUlSQS to interconnect said correctmg cncmt to said toll line to remove the noise lmpulses.

12. In combination, a toll line over which speech and .noise frequencies are transmitted, a normal line, a repeater connecting said lines, correcting circuits permanently connected tosaid repeater and said normal line, each of said circuits being tuned to a particular frequency corresponding to a noise fre- ;quency present in said toll line, means for associating said correcting circuits to said toll line, and a plurality of tuned relays bridged across said toll line, each of said relays being provided with a tuned reed operated by noise frequencies present in said toll line, whereby on] r the tuned correcting circuits corresponding to the frequenlc ies present in said line are connected to said me. I: v 13. In combination, a line over which speech and noise impulses are transmitted, a normal line, a correcting circuit normally line, and automatic associate said correcting circuits to said line to neutralize said noise impulses.

14. In combination, a line over which speech and noise impulses are transmitted, a normal line, a correcting circuit. and a me chanicully tuned reed. said reed being automatically vibratedby said noise impulses to connect said correcting circuit to said line, said circuit changing the phase of said impulses and impressing said changed impulses on the output of said connecting C11- cuit to neutralize the noise in said line.

In witness whereof, I hereunto subscribe my name this 28th day of December, A. D.,

. IRA G. WILSON. 

